Impact of anthropogenic emissions on biogenic secondary organic aerosol: observation in the Pearl River Delta, southern China

Zhang, Yu-Qing; Chen, Duo-Hong; Ding, Xiang; Li, Jun; Zhang, Tao; Wang, Jun-Qi; Cheng, Qian; Jiang, Hao; Song, Wei; Ou, Yu-Bo; Ye, Peng-Lin; Zhang, Gan; Wang, Xin-Ming

Secondary organic aerosol (SOA) formation from biogenic precursors is affected by anthropogenic emissions, which are not well understood in polluted areas. In this study, we accomplished a year-round campaign at nine sites in polluted areas located in the Pearl River Delta (PRD) region during 2015. We measured typical biogenic SOA (BSOA) tracers from isoprene, monoterpenes, and inline-formulaβ-caryophyllene, as well as major gaseous and particulate pollutants and investigated the impact of anthropogenic pollutants on BSOA formation. The concentrations of BSOA tracers were in the range of 45.4 to 109 ng minline-formula−3 with the majority composed of products from monoterpenes (SOAinline-formulaM, inline-formula47.2±9.29 ng minline-formula−3), isoprene (SOAinline-formulaI, inline-formula23.1±10.8 ng minline-formula−3), and inline-formulaβ-caryophyllene (SOAinline-formulaC, inline-formula3.85±1.75 ng minline-formula−3). We found that atmospheric oxidants, inline-formulaOx (inline-formulaO3 plus inline-formulaNO2), and sulfate correlated well with later-generation SOAinline-formulaM tracers, but this was not the case for first-generation SOAinline-formulaM products. This suggested that high inline-formulaOx and sulfate levels could promote the formation of later-generation SOAinline-formulaM products, which probably led to the relatively aged SOAinline-formulaM that we observed in the PRD. For the SOAinline-formulaI tracers, both 2-methylglyceric acid (NO/inline-formulaNO2-channel product) and the ratio of 2-methylglyceric acid to 2-methyltetrols (inline-formulaHO2-channel products) exhibit inline-formulaNOx dependence, indicating the significant impact of inline-formulaNOx on SOAinline-formulaI formation pathways. The SOAinline-formulaC tracer was elevated in winter at all sites and was positively correlated with levoglucosan, inline-formulaOx, and sulfate. Thus, the unexpected increase in SOAinline-formulaC in wintertime might be highly associated with the enhancement of biomass burning, inline-formulaO3 chemistry, and the sulfate component in the PRD. The BSOAs that were estimated using the SOA tracer approach showed the highest concentration in fall and the lowest concentration in spring with an annual average concentration of inline-formula1.68±0.40inline-formulaµg minline-formula−3. SOAinline-formulaM dominated the BSOA mass all year round. We also found that BSOA correlated well with sulfate and inline-formulaOx. This implied a significant effect from anthropogenic pollutants on BSOA formation and highlighted that we could reduce BSOA by controlling the anthropogenic emissions of sulfate and inline-formulaOx precursors in polluted regions.

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Zhang, Yu-Qing / Chen, Duo-Hong / Ding, Xiang / et al: Impact of anthropogenic emissions on biogenic secondary organic aerosol: observation in the Pearl River Delta, southern China. 2019. Copernicus Publications.

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